A sentient being is a being who is subjectively aware; a being who has interests; that is, a being who prefers, desires, or wants. Those interests do not have to be anything like human interests. If a being has some kind of mind that can experience frustration or satisfaction of whatever interests that being has, then the being is sentient.

We engage in speciesist thinking when we claim that a being must have a humanlike mind to count morally. That is, it is speciesist to claim that a being must have a reflective sense of self awareness, or conceptual thought, or the general ability to experience life in the way that humans do in order to have the moral right not to be used as a resource. As long as there is someone there who is subjectively aware and who, in that being’s own way, cares about what happens to him or to her, that is all that is necessary to have the moral right not to be used as a resource.

Is there uncertainty as to where the line is between sentient and nonsentient? Of course there is. It is, however, clear beyond any doubt that all of the animals that we routinely exploit–the fish, cows, pigs, sheep, goats, chickens and other birds, lobsters, etc. are sentient. So we know everything we need to know to make the moral decision to stop eating, wearing, or using those animals.

Can we say with as much certainty as is possible in any empirical matter that plants are not sentient? Yes, of course we can. Plants are alive; plants react to stimuli. But plants do not respond through any conscious process. That is, there is no reason whatsoever to believe that plants have any sort of mind that cares about what happens to the plant.

People often say that I regard insects as not sentient. That is not accurate. I do not know whether insects are sentient. I err on the side of sentience and I do not intentionally kill them. Indeed, I exercise caution when I walk so as not to kill or injure them. I do not know whether clams or other mollusks are sentient although I err in favor of sentience and do not eat them or buy products made from them.

But I repeat: not knowing where to draw the line does not mean that we don’t know enough right now to be absolutely clear that we have a moral obligation not to eat, wear, or use animals, and that veganism must be the moral baseline of a movement that seeks justice for nonhuman animals.

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If you are not vegan, please go vegan. Veganism is all about nonviolence. First and foremost, it’s about nonviolence to other sentient beings. But it’s also about nonviolence to the earth and nonviolence to yourself.

A number of people have written to me in the past day asking me whether I consider eating clams to be vegan. These inquiries were prompted by the video linked to above.

No, I do not regard consuming these nonhumans to be consistent with being a vegan.

In the case of plants, we can be as certain about nonsentience as as we can be about anything. The case for nonsentience in the case of clams, oysters, etc., is not certain and, therefore, it seems to me to make good moral sense to have a presumption in favor of sentience and against exploitation. And there are other mollusks (cephalopods, such as the squid, octopus, etc.) who are more neurologically developed and where it is clear that there is sentience. So I regard it as good moral sense to presume in favor of the sentience of clams, oysters, and scallops and all mollusks (including snails) and to not eat them or otherwise exploit them as human resources.